Lubricating greases are widely used in industrial and commercial applications. They are used whenever two or more solid surfaces move in close contact. Bearings, suspension joints, gearboxes, and machinery slides are a few of the many used. Any rotating or sliding motion of two solid surfaces working together to accomplish a mechanical purpose uses a lubricating grease.
Some applications require that a lubricating grease be used on an everyday basis, e.g. to repack bearing surfaces. Some applications such as some ball joints have a grease fitting for periodic addition of the grease. Still other applications such as sealed ball joints are considered to be “lubed for life”. However, the grease in a sealed ball joint can break down and lose its lubricating characteristic. Care must be taken to ensure the grease used in any part which is sealed be formulated with consideration given to the part's operating use conditions.
Lubricating greases are generally semi-solid in form. A base oil thickened with a thixotropic agent is the major component of such greases. The lubricating greases initially have a high viscosity. After sufficient force is applied, such as encountered by moving gears in a gearbox, the viscosity is reduced. There can be sufficient enough a drop in the viscosity that it approaches that of the base oil.
One base oil is a mineral oil produced by refining crude oil. Mineral oils are most commonly used in lubricating greases. Synthetic oils are commonly used as the base oil for extreme temperature applications. The synthetic oils are produced through chemical synthesis. They typically are polyalphaolefins, esters such as diesters, polyesters, polyolesters, alkylated napthalenes, alkylated benzenes, etc., or hydrocracked/hydroisomerized mineral oils. Semi-synthetic base oils are also available. They are simply blends of mineral oil and synthetic oil.
Thixotropic agents thicken base oils to a semi-solid from. Such agents typically are metallic soaps, metal soaps plus complexing agents and other materials including organo clay, polyurea, silica, carbon black and organic polymers.
It is very common to add one or more performance additives to a lubricating grease depending on the grease's use. Thus, anti-rust agents are added for alleviating corrosion, anti-oxidants to prolong the base oil's life, and others. Enhancing the inherent lubrication effect of the base oil in the lubricating grease is always a desired objective. The better the lubricating property of the base oil, the longer the life of any mechanical device and the more operation efficiency. Each benefit provides a lower cost of operation. The need for enhanced lubrication is particularly noted under heavy work loads that increase the grease's operating temperature and pressure. For example, race cars running at high speeds require greases that effectively operate at temperatures up to about 2100 degrees Fahrenheit and extreme pressures. This temperature is above that which liquid components can operate. Solid lubricants are needed for such temperatures and beyond. Certain industrial equipment with heavy work loads also experience high temperatures and pressures during use that challenge known lubricating greases. Wheeled carts or conveyor belt wheels which carry workpieces through an oven for processing can experience extreme temperatures and force pressures.
In accord with a need, there has been developed a blend of solid components which allows a lubricating grease composition to withstand excessive temperatures and pressures. The blend of components functions effectively in greases at normal operating conditions as well as extreme operating conditions.